Spent nuclear fuel elements are processed to separate uranium, plutonium and fission products therein by a continuous, countercurrent solvent extraction operation commonly known as the Purex process. This process comprises the basic steps of (1) separation of fission products from U and Pu, (2) separation of U from Pu, and (3) further decontamination and concentration of U and Pu product streams. More specifically, U and Pu are extracted from a nitric acid solution (used to dissolve the spent fuel elements) into an organic phase containing tributyl phosphate (TBP) and an organic diluent such as dodecane, leaving most fission products in the aqueous phase. However, technetium is produced in large quantities in nuclear reactors, and whenever both UO.sub.2.sup.2+ and the pertechnetate ion (TcO.sub.4.sup.-) are in the same solution, a complex containing both UO.sub.2.sup.2+ and TcO.sub.4.sup.- is formed which prevents separation of uranium from the technetium by the conventional steps of the Purex process.
When reprocessed U containing Tc is recycled to gaseous diffusion plants for enrichment, accumulation of Tc in process equipment causes various operational problems. Current methods for removing Tc from reprocessed U are employed only on the feed to gaseous diffusion plants and involve the sorption of gaseous technetium fluorides on solid traps. It would be more convenient to separate U and Tc in association with the chemical steps of the Purex process.